Yes, @Gordon0 and @Yadira22, this is what seems like the normal thing to do, especially for a superhost. And I'm already paying the normal price, equivalent to 400USD for 2 nights, so I don't feel I'm completely getting a steal for this tiny flat (even though it is during a major event).
Anyway, based on what I've read here and elsewhere, it seems as though most advice is telling me to have the host cancel if she so chooses to do. Unfortunately, as of the last email exchange, this host seems adamant that I should cancel. Today, the 48hr free cancel expires, so I we'll see what happens.
I should be clear: this is an entire, separate (very small) flat in an apartment block (in which the host owns other units available on Airbnb) that I've booked.